I am planning on getting two ducklings in a couple of weeks time, one Cayuga and one Welsh Harlequin, although I have been trawling through this forum for about a week now I still have some questions and I would appreciate it if one of you would be kind enough to shed some light on a few things 
obviously due to the time of year by time the ducklings are 4 - 6 weeks old its going be pretty cold here, what age should is good to let them reside permanently outside?
I'm struggling to locate Duck starter crumbs here in the UK, I have seen some advertised for Ducks and Geese and I think the brand was "Smallholder" or something along those lines, any suggestions on where to find some if this isn't acceptable?
Another thing is that most places say that they are unable to sex the ducklings, I know vent sexing can cause issues so maybe this is why, but i'm worried that I will end up with one drake and one duck, obviously after raising these guys I will not be able to part with them but I think the amout of ducks I can realistically keep is around 4 but two would be much better and obviously buying more would also not guarantee more females and could make the situation worse, any advice?

obviously due to the time of year by time the ducklings are 4 - 6 weeks old its going be pretty cold here, what age should is good to let them reside permanently outside?
I'm struggling to locate Duck starter crumbs here in the UK, I have seen some advertised for Ducks and Geese and I think the brand was "Smallholder" or something along those lines, any suggestions on where to find some if this isn't acceptable?
Another thing is that most places say that they are unable to sex the ducklings, I know vent sexing can cause issues so maybe this is why, but i'm worried that I will end up with one drake and one duck, obviously after raising these guys I will not be able to part with them but I think the amout of ducks I can realistically keep is around 4 but two would be much better and obviously buying more would also not guarantee more females and could make the situation worse, any advice?